Monitoring camera device capable of adjusting the changeover between standard time and day light saving time

ABSTRACT

A monitoring camera device adds image capturing time data to image data which is successive with respect to time, and stores the image data on a recording medium. A plurality of directories are prepared on the recording medium for containing a predetermined number of items of image data, and are each named according to a directory naming rule, such that a portion of the name is made different when the directory is prepared during the period of standard time and when the directory is prepared during the period of daylight saving time. The directory also has attached thereto directory preparing time data indicating the time when the directory is prepared. 
     The camera device judges whether each of the directories is prepared during the period of the standard time or during the period of daylight saving time with reference to the name of the directory, and judges the order of directory preparing times using the time indicated by the directory preparing data of the directory when the directory is found to have been prepared during the period of the standard time, or using a value obtained by subtracting a time correction value from the time indicated by the directory preparing data of the directory when the directory is found to have been prepared during the period of daylight saving time.

TECHNICAL FIELD

The present invention relates to surveillance or monitoring cameradevices for recording still image data which is successive with respectto time along with image capturing time information, and moreparticularly to monitoring camera devices adapted for daylight savingtime and to an image data management method for such monitoring cameradevices.

BACKGROUND ART

Common surveillance or monitoring camera devices are systems comprisinga digital still camera and having the function of continually capturingstill images at intervals of a predetermined period of time. The stillimage data obtained is stored on a recording medium with image capturingtime data added thereto. Useful as recording media are hard disks,optical disks, etc. of great capacity which are accessible randomly forstoring still image data which is successive with respect to time. Themonitoring camera device erases the image data of the oldest imagecapturing time when the quantity of image data stored approaches thecapacity of the recording medium or the recording capacity set on therecording medium, in order to obviate the likelihood of the cameradevice becoming unable to capture images upon the quantity of stillimage data stored exceeding the capacity of the recording medium. Thisenables the camera device to continually capture still images atintervals of a predetermined period of time unless the user performs anending manipulation.

The monitoring camera device has the same image capturing mechanism ascommon digital still cameras, and the still image data to be recorded isprepared according to a known data compressing method such as the JPEGmethod. The still image data obtained by capturing images is storedtemporarily in a buffer memory within the camera device, and imagecapturing time data is added to the image data, which is then recordedon the recording medium successively. The camera device manages theimage data with reference to the image capturing time data. Theabove-mentioned oldest image data is erased also with reference to theimage capturing time. However, the data management with reference to theimage capturing time data is likely to involve trouble due to the systemof daylight saving time.

Daylight saving time is a system wherein timepieces are advanced by apredetermined period of time from the standard time during a specifiedperiod of from spring to fall. Daylight saving time is presently adoptedby at least seventy countries. In the U.S., for example, the period ofdaylight saving time starts at 2 a.m. on the first Sunday of April andends at 2 a.m. on the last Sunday of October, and during this period,timepieces are advanced by one hour. Stated more specifically withreference to FIG. 12, the period of daylight saving time in 2001 ADstarts at 2 a.m. on the first Sunday of April, i.e., April 1.Accordingly, the time of day following April 1, 1:59 a.m. is not 2 a.m.but 3 a.m. The period of daylight saving time ends at 2 a.m. on the lastSunday of October, i.e., October 28. The time of day following October28, 1:59 a.m. is not 2 a.m. but returns to 1 a.m.

Monitoring camera devices comprise a timepiece adapted for daylightsaving time and are given image capturing time data by the timepiece.During the period of daylight saving time, the timepiece adapted forthis system calculates daylight saving time by adding a predeterminedtime correction value to the standard time. Such a timepiece needs tohave set therein information serving to provide a basis for judgingwhether the current time is within the period of daylight saving time.Generally provided as this information are conditions for a transitionfrom the standard time to daylight saving time (hereinafter referred toas “DST transition conditions”) which are determined for each year andwhich comprise the starting time and ending time of the period ofdaylight saving time. In the case of the U.S. in 2001 AD shown in FIG.12, determined as the DST transition conditions are “the first Sunday(1^(st))of April, 2 a.m.” as the starting time of the period of daylightsaving time and “the last Sunday (28^(th)) of October, 2 a.m.” as theending time of the period. The starting time is expressed in thestandard time, and the ending time in daylight saving time.

The surveillance or monitoring camera device is intended forsurveillance or monitoring, and successively and continually recordsimage data at intervals of a predetermined period of time, so that imagecapturing time data for giving information as to the image capturingtime or times is important. By erasing the oldest data from the recordedimage data, the monitoring camera device is capable of continuallycapturing still images at intervals of a predetermined period of timeand recording the images obtained. Accordingly, the image capturing timedata needs to be added to the image data in corresponding relation withthe image capturing order. No problem will arise if the system ofdaylight saving time is not adopted. If the image capturing time dataaccording to the standard time is added to the image data, the imagecapturing order of the image data can be recognized by reference to theimage capturing time data. However, in the case where the system ofdaylight saving time is adopted, problems will arise because whendaylight saving time is changed over to the standard time, a situationwill occur wherein time reverts.

With reference to the case of the U.S. shown in FIG. 12 as an example,at the current time of October 28, 2 a.m. in daylight saving time, thetime of day output by timepieces returns to the standard time fromdaylight saving time. The time of day in the standard time is thenOctober 28, 1 a.m. Thus the change of summer time to the standard timeinvolves a lap of time zones (after 1 a.m. and before 2 a.m.).

If times lap which are indicated by the items of image capturing timedata corresponding respectively to an item of image data and anotheritem of image data which are obtained by the monitoring camera device,it is impossible to recognize the order of image capturing timescorresponding to the respective items of image data. This gives rise tothe problem that the monitoring camera device is unable to continue tocapture and record images by erasing the oldest data from the recordedimage data.

The present invention provides a monitoring camera device which isadapted to continually and successively capture and record images byrecognizing the order of image capturing times corresponding to storedimage data and erasing old image data, even if a lap of times occurs dueto a changeover from daylight saving time to the standard time, and animage data management method for the monitoring camera device.

DISCLOSURE OF THE INVENTION

The present invention provides a monitoring camera device wherein imagecapturing time data is added to image data which is successive withrespect to time, and the image data is stored on a recording medium. Themonitoring camera device is characterized in that a plurality ofdirectories are prepared on the recording medium for containing apredetermined number of items of image data, each of the directoriesbeing given a name according to a directory naming rule, a portion ofthe name being different when the directory is prepared during theperiod of standard time and when the directory is prepared during theperiod of daylight saving time.

In the monitoring camera device of the invention, each of thedirectories has attached thereto directory preparing time dataindicating the time when the directory is prepared.

The monitoring camera device of the invention comprises means forjudging whether each of the directories is prepared during the period ofthe standard time or during the period of daylight saving time withreference to the name of the directory, and judging the order ofdirectory preparing times using the time indicated by the directorypreparing data of the directory when the directory is found to have beenprepared during the period of the standard time, or using a valueobtained by subtracting a time correction value from the time indicatedby the directory preparing data of the directory when the directory isfound to have been prepared during the period of daylight saving time.

The monitoring camera device of the invention captures and recordsimages while erasing the directory prepared earliest with reference tothe result of judging the directory preparing time order.

The present invention provides an image data management method for amonitoring camera device for continually capturing and recording imagesby preparing a plurality of directories on a recording medium, addingimage capturing time data to image data which is successive withrespective to time and storing the image data under the directories. Theimage data management method comprises the steps of: preparingdirectories each having a name given thereto and directory preparingtime data attached thereto and indicating the time when the directory isprepared, a portion of the name being different when the directory isprepared during the period of standard time and when the directory isprepared during the period of daylight saving time; judging whether eachof the directories is prepared during the period of the standard time orduring the period of daylight saving time with reference to the name ofthe directory; judging the order of directory preparing times using thetime indicated by the directory preparing data of the directory when thedirectory is found to have been prepared during the period of thestandard time, or using a value obtained by subtracting a timecorrection value from the time indicated by the directory preparing dataof the directory when the directory is found to have been preparedduring the period of daylight saving time; and erasing the directoryprepared earliest along with the image data under the earliest directorywith reference to the result of judging the directory preparing timeorder in the case where the number of directors has reached an upperlimit value.

According to the present invention, the directory naming rule is soprescribed that a portion of the name of the directory is made differentwhen the directory is prepared during the period of standard time andwhen the directory is prepared during the period of daylight savingtime. Therefore, even if image capturing time data is provided inconformity with the system of daylight saving time, the order of imagecapturing times of the image data can be recognized with reference tothe names of the directories. The directory which is prepared earliestis erased along with the image data under this directory, whereby arecording area is made available for the image data to be stored anew.This ensures a continual image capturing and recording operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a monitoring camera device embodying theinvention;

FIG. 2 is a diagram showing a representation on the display screen of amonitor when a time of day is set;

FIG. 3 is a diagram showing a representation on the display screen ofthe monitor when the DST transition conditions are set;

FIG. 4 is a flow chart showing an operation of a timepiece according tothe invention;

FIG. 5A is a diagram for illustrating data structure on a hard disk foruse in the monitoring camera device embodying the invention;

FIG. 5B is a diagram for illustrating directories prepared on the harddisk for use in the monitoring camera device embodying the invention anddirectory preparing time data;

FIG. 6 is a flow chart showing image processing of the monitoring cameradevice embodying the invention;

FIG. 7 is a flow chart showing a hard disk recording procedure of themonitoring camera device embodying the invention;

FIG. 8 is a flow chart showing a directory checking procedure of themonitoring camera device embodying the invention;

FIG. 9 is a flow chart showing a directory erasing procedure of themonitoring camera device embodying the invention;

FIG. 10 is a flow chart showing a standard time recording procedure ofthe monitoring camera device embodying the invention;

FIG. 11 is a flow chart showing a daylight saving time recordingprocedure of the monitoring camera device embodying the invention; and

FIG. 12 is a diagram for illustrating a system of daylight saving time.

BEST MODE OF CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below in detailwith reference to the drawings. A system of daylight saving time will bedescribed with reference to the case of the U.S. in 2001 shown in FIG.12.

FIG. 1 is a block diagram of an embodiment of the invention, i.e., amonitoring camera device. This camera device comprises a timepiece 31adapted for daylight saving time. An image pickup unit 1 comprises anoptical lens, diagram mechanism and solid image pickup element such asCCD. The image pickup unit 1 is controlled by an image pickup controlcircuit 9 which is operable in response to a control signal from a CPU11. An A/D converter 3 converts an analog image signal input from theimage pickup unit 1 to a digital image signal. The digital image signalis processed by a signal processing circuit 5 for color separation,gamma correction, white balance adjustment, etc. The resulting digitalimage data is compressed by the CPU 11 and stored in a memory buffer 21as compressed data. According to the present embodiment, the image datais compressed by the JPEG method. CPU 11 performs calculations ofdaylight saving time, processing based on the DST transition conditions,etc. Connected to the CPU 11 are a ROM 27 having stored therein programsprescribing the processing to be executed by the CPU 11, and EEPROM 29having the DST transition conditions. The CPU 11, ROM 27 and EEPROM 29constitute the timepiece 31 along with a standard clock 19 foroutputting standard time data. The standard clock 19 delivers standardtime data to the CPU 11 in a predetermined cycle at all times.

The compressed image data stored in the memory buffer 21 has attachedthereto, as subinformation, image capturing time data output from theCPU 11 when images are captured. The compressed image data is stored viathe CPU 11 on a hard disk 7 which is a recording medium randomlyaccessible. The CPU 11 processes the compressed image data on the harddisk 7 for the expansion of the data when the compressed data is to bereproduced in the initial form. A video encoder 13 adds a synchronizingsignal and color burst signal to the digital image signal resulting fromexpansion of the data. The image signal is thereafter converted to ananalog image signal by a D/A converter 15. A monitor 17 displays imagesbased on the analog image signal. The monitor 17 serves also as adisplay for indicating to the user various settings, especially settingsof times of day and the DST transition conditions.

A system controller 23 controls the CPU 11 in response to themanipulation of manual buttons 25. When suitably manipulated, manualbuttons 25 set the timepiece 31 in a time setting mode. In the timesetting mode, particulars about a time setting are presented on thescreen of the monitor 17 as shown in FIG. 2. While watching the monitor17, the user manipulates manual buttons 25 to input year, month, day,hours and minutes. These items are entered by manipulating numeralbuttons, decision button, cancel button, etc. included among the manualbuttons 25. In place of or in addition to the numeral buttons, themanual buttons 25 include a cross button for moving a cursor on thescreen and an up-down button for increasing or decreasing a number onthe screen. Items may be entered using these buttons. When a time isset, the timepiece 31 starts to count time at the set time.

When the timepiece 31 is set in a daylight saving time setting mode bymanipulating manual buttons 25, particulars about a daylight saving timesetting are presented on the screen of the monitor 17 as shown in FIG.3. While watching the monitor 17, the user enters the starting time andending time of daylight saving time by manipulating manual buttons 25.In the daylight saving time setting mode, it is possible to determinewhether the DST transition conditions set are valid. When the setting ofDST transition conditions is made “off,” the timepiece 31 outputsstandard time even during the period of daylight saving time. In thestate shown in FIG. 3, the DST transition conditions are “on,” thedaylight saving time starting time is set on the first Sunday of Aprilat 2 a.m. as expressed in the standard time, and the daylight savingtime ending time is set on the last Sunday of October at 2 a.m. asexpressed in daylight saving time.

As previously described, data as to the year is set in the time settingmode. In the case shown in FIG. 2, “2001” is set as year data. In thedaylight saving time setting mode, the dates of the daylight saving timestarting time and ending time are not shown in numerical values. Withreference to the year data, and data as to the calendar for tens ofyears stored in the ROM 27, the CPU 11 calculates that the first Sundayof April is April 1, and that the last Sunday of October is October 28.The calculated items of data as to the daylight saving time startingtime and ending time are stored in the EEPROM 29.

Next, the time calculating operation of the timepiece 31 will bedescribed with reference to FIG. 4, with attention directed mainly tothe processing to be performed by the CPU 11. The CPU 11 calculates timeas interrupt processing at intervals of a predetermined period of time,every time an image is captured, every time compressed image data isstored on the hard disk 7, and every time a directory as to compressedimage data to be stored is prepared on the hard disk 7. In thebeginning, standard time data output from the standard clock 19 is fedto the CPU 11, which in turn inquires whether the standard timeindicated by the data is included in the daylight saving time zone (S1).The term “daylight saving time zone” refers to the daylight saving timestarting time and the subsequent time zone before the daylight savingtime ending time, as expressed in the standard time (not inclusive ofthe ending time). In the illustrated case of FIG. 12, the daylightsaving time starting time according to the standard time is April 1, 2a.m., and the daylight saving time ending time according to the standardtime is October 28, 1 a.m. The CPU 11 inquires whether the standard timeindicated by the data is included in the time zone of from April 1, 2a.m. to October 28, 0:59:59 a.m. When the answer is negative, thetimepiece 31 adopts the standard time data output by the standard clock19 as it is as calculated time data (S2). The time data output from thetimepiece when an image is captured is added to the image data ordisplay data on the monitor 17 as image capturing time data. The timedata output from the timepiece 31 when a directory is prepared as to thecompressed image data is added to the directory as directory preparingtime data.

When the answer to the inquiry of step S1 is affirmative, the CPU 11adds a time correction value for use during the period of daylightsaving time to the standard time to calculate daylight saving time, andoutputs daylight saving time data indicating the daylight saving time(S3). The time correction value for use during the period of daylightsaving time refers to the time difference value between the standardtime and daylight saving time. In the illustrated case of FIG. 12, thetime correction value is 1 hour. The timepiece adopts the daylightsaving time data as the calculating time data (S4) As in the previouscase, the time data is used as image capturing time data and directorypreparing time data.

In a usual recording mode, the monitoring camera device continues tocapture still images at intervals of a predetermined period of time, andthe images obtained are successively recorded on the hard disk. FIG. 5shows the logic data structure of the hard disk 7 for use as a recordingmedium in the usual recording mode. Positioned below the root directoryis a first directory named “ALARM”, below which there are seconddirectories (“100ALARM01,” “101ALARM01,” etc.) containing the compressedimage data obtained by image capturing. With reference to FIG. 5(A), thesecond directories contain JPEG files in units of 900 files. Thecompressed image data is given file names according to a specifiednaming rule, and the last four characters in the file names(IMAGE0001-0900 are consecutive numbers given according to the imagerecording order. The second directories are similar in the names givento the image files. Accordingly, compressed image data having the samefile name is included in each directory. According to the presentembodiment, the camera device captures and records images at a rate of 3fps (frames per second), i.e., three frames per second, so thatcompressed image data obtained for a monitoring period of 5 minutes iscontained in each second directory.

The camera device performs compressed image data management in units ofsecond directories. As previously described, each secondary directoryhas directory preparing time data added thereto. When the quantity ofcompressed image data stored on the hard disk 7 is about to exceed apredetermined upper limit in the usual recording mode, the camera deviceerases the second directory prepared earliest and the whole compressedimage data in this second directory. This provides on the hard disk 7 adata recording area for storing compressed image data obtained anew.

According to the present embodiment, the quantity of compressed imagedata to be stored on the hard disk 7 in the usual recording mode isrestricted to an upper limit which is a quantity corresponding to 60minutes in terms of monitoring time period. Since there are 900compressed image files in each second directory, this quantity of datacorresponds to 12 second directories. The timing with which the erasureof the second directory prepared earliest (the oldest second directory)starts is set at the time when the first item of compressed image datastarts in the latest 12th second directory. When compressed image datais to be placed into the 12th second directory, the oldest seconddirectory and all the compressed image data contained therein have beenerased. Since this procedure is repeated, there is no likelihood thatthe quantity of compressed image data stored on the hard disk 7 willexceed the upper limit value.

With the camera device of the present invention, the second directoryfor containing compressed image data is named according to the followingrule. The first portion of the name of second directory is in the formof a number. In the case where a new second directory is to be preparedon the hard disk 7, the name to be given to the new second directory ismade by adding the FIG. 1 to the first portion of the name of the seconddirectory having the latest directory preparing time data (the directorywherein compressed image data is placed immediately before the currenttime). In the case of the data structure shown in FIG. 5, the seconddirectory preparing time goes on from above downward. Thus, the firstthree characters of the names of second directories read “100,” “101,”“102,” . . . “111,” as time goes on. The three figures in the firstportions are used in circulation or repeatedly. There is an upper limitvalue for the number represented by these figures which value isdependent on the predetermined recording capacity. When a seconddirectory is prepared which has first three characters representing theupper limit value, the number represented by the first three charactersin the name of the second directory to be prepared next has the smallestvalue. In the case of the present embodiment, prepared subsequently tothe second directory named with the first three characters of “111” isthe second directory named with “100” again.

The rear portion of the name of the second directory also has figures.This portion of the name of a second directory prepared during theperiod of the standard time differs from the corresponding portion ofthe name of a second directory prepared during the period of daylightsaving time in figures. In other words, different figures are used forthis portion when the directory preparing time of the second directoryis the standard time and when the preparing time is daylight savingtime. With reference to FIG. 5B, the years, months, days, hours, minutesand seconds given at the right of second directories are timesindicating by the preparing time data of the respective seconddirectories. (Like image capturing time data is added also to thecompressed image data files shown at the right side of the FIG. 5A.) Inthe case of the data structure shown in FIG. 5B, the first two seconddirectories are prepared during the period of daylight saving time, andthe last two characters of the name of each of these directories are“01.” The other second directories are prepared during the period of thestandard time, and the last two characters of the name of each of thesedirectories are “00.”

Next, the image data recording operation of the monitoring camera deviceof the present embodiment will be described with reference to the flowchart of FIGS. 6 to 11. The camera device has installed in the CPU 11 areal time OS capable of performing a multitask processing. Accordingly,the image pickup processing with use of the image pickup unit 1, thestorage processing of compressed image data on the hard disk 7 anderasure processing of the compressed image data are performedconcurrently. Thus, even during processing for the erasure of compressedimage data, feeding of digital image data to the CPU 11, imageprocessing and compression processing for digital image data by the CPU11, and the processing for storing the resulting compressed image datain the memory buffer are conducted.

FIG. 6 is a flow chart showing image pickup processing using the imagepickup unit 1. When image pickup processing is started, analog imagedata is read from the solid image pickup element, such as CCD, providedin the unit 1 (S5). The analog image signal is converted to digitalimage data, which is subjected to image processing by the signalprocessing circuit 5 for color separation, gamma correction and whitebalance adjustment (S6). The digital image data processed is furtherprocessed for compression by CPU 11 according to the JPEG method, andthe compressed image data is then stored in the memory buffer 21 (S7).In the usual recording mode, the above procedure is repeated at apredetermined frame rate, i.e., at 3 fps according to the presentembodiment.

FIG. 7 is a flow chart showing a procedure for storing the compressedimage data on the hard disk 7 in the usual recording mode. The usergives a command to start image recording in the usual recording mode tothe CPU 11 via the system controller 23 by depressing manual buttons 25,whereupon the second directories already prepared on the hard disk 7 arechecked (S11). The subsequent steps will be described later.Incidentally, the image pickup processing is effected in preference tothe procedure shown in FIG. 7. Stated more specifically, the storage ofthe compressed image data on the hard disk 7 to be described later isperformed during a period other than the period of operation of the CPU11 for executing the image pickup processing of FIG. 6.

FIG. 8 is a flow chart showing the checking procedure. First, a list ofsecond directories existing in a recording area provided on the harddisk 7 for the usual recording mode is prepared by checking a filemanagement region (FAT) of the hard disk 7 (S111). Next, reference ismade to the names of second directories listed up (S112), and an inquiryis made as to whether each of the directories is prepared during theperiod of daylight saving time with reference to the last two digits inthe names of the second directories (S113). When the last digits of thename are “00,” the second directory concerned is found to have beenprepared during the period of the standard time. The time indicated bythe directory preparing time data of the second directory is adopted asit is as time data for preparing a directory time order table withoutchanging the data (S117). On the other hand, if the last portion of thename of the second directory is “01,” this indicates that the seconddirectory concerned is prepared during the period of daylight savingtime. The time correction value which is a value of time differencebetween the standard time and daylight saving time is subtracted fromthe second directory preparing time to obtain a time, which is adoptedas time data for preparing the directory time order table (S119) In theillustrated case of FIG. 12, 1 hour is subtracted as the time correctionvalue.

Next, the directory time order table is prepared with reference to thetime data obtained in step S117 and/or step S119 (S121). In the casewhere the second directory is prepared during the period of daylightsaving time as described above, the time obtained by subtracting thetime correction value from the second directory preparing time is usedfor preparing the directory time order table in step S119, so that thetable prepared is correct even if the preparing time indicated by thedirectory preparing time data as to the second directory prepared duringthe period of daylight saving time overlaps the preparing time indicatedby like data as to the second directory prepared during the period ofthe standard time.

When steps S113 to S121 are performed for all the second directoriesgiven in the list prepared in step S111, the step S11 shown in FIG. 7,i.e., the procedure for checking the second directories on the hard disk7 is completed (S123).

FIG. 7 will be referred to again. When step S11 is completed, an inquiryis made as to whether the memory buffer 21 has compressed image data notstored on the hard disk 7 (S13) If the memory buffer 21 has compressedimage data not stored on the disk 7, step S17 and the following stepsare performed, whereas if there is no compressed image data, step S29and the following steps are performed (S15).

If the memory buffer 21 has the compressed image data remaining unstoredon the hard disk 7 (S15), reference is made to the directory time ordertable prepared in step S121 (S17). An inquiry is then made as to whetherthe number of second directories below the first directory (“ALARM”) is12 (S19) When the number of second directories is 12, the real time OSof the CPU 11 is given a command to erase the second directory which isprepared earliest (S21). The real time OS given the command to erase thedirectory erases the second directory shown in FIG. 9. The oldestdirectory is specified (S211) with reference to the directory time ordertable, and is erased (S213). With the erasure of the second directory,the compressed image files contained therein are also erased.

On the other hand, if the number of second directories is found to beless than 12 in FIG. 7, step S19, the image capturing time data added tothe compressed image data is referred to, and an inquiry is made as towhether the image capturing time is within the daylight saving time zoneaccording to the standard time counted by the standard clock 19, namelyas to whether the image capturing time is after the daylight saving timestarting time as expressed in the standard time and before the daylightsaving time ending time as expressed in the standard time (S23). Unlessthe image capturing time is within the daylight saving time zone, thereal time OS of the CPU 11 is given a command to conduct a standard timerecording operation. (S25). When the image capturing time is within thedaylight saving time zone, the real time OS of the CPU 11 is given acommand to conduct a daylight saving time recording operation (S27).

FIG. 10 is a flow chart showing a standard time recording procedure.First, an inquiry is made as to whether the compressed image files underthe second directory prepared last are less than 900 in number (S251).Thus, an inquiry is made as to whether a compressed image file can beadded to the second directory. In the case where the number ofcompressed image files is less than 900, compressed image data can bestored on the hard disk 7 without preparing a new second directory(S253). The compressed image data is contained in the second directorywhich is prepared last, whereby the standard time recording procedure iscompleted.

When the compressed image files under the second directory prepared lastare found to be 900 in number in step S251, a new second directory isprepared on the hard disk 7 with directory preparing time data added tothe directory (S255). At this time, a name is given to the new seconddirectory according to the naming rule described with reference to FIG.5. Stated more specifically, the first number of the name is a valueobtained by adding 1 to like number in the name of the second directoryprepared last, and the last digits of the name are “00” (for example,“103ALARM00”). The time indicated by preparing time data added to thenew second directory is used as it is without being changed as time datafor preparing the time order table (S257). The directory time ordertable is updated so as to include information as to the second directory(S259), and the compressed image data is stored on the hard disk 7 so asto be positioned under the second directory (S253), whereby the standardtime recording procedure is completed.

When the real time OS of CPU 11 is given the command to conduct adaylight saving time recording operation in step S27 of FIG. 7, on theother hand, this operation is performed as shown in FIG. 11. First, aninquiry is made as to whether the compressed image files under thesecond directory prepared last area less than 900 in number (S271). Ifthe inquiry is answered in the affirmative, compressed image data isstored on the hard disk 7 so as to be contained under the seconddirectory (S273), whereby the daylight saving time recording operationis completed.

When the compressed image files under the second directory prepared lastare found to be 900 in number in step S271, a new second directory isprepared on the hard disk 7 with directory preparing time data attachedto the directory (S275). At this time, the new second directory is namedaccording to the naming rule described with reference to FIG. 5. Statedmore specifically, the first number of the name is a value obtained byadding 1 to like number in the name of the second directory preparedlast, and the last digits of the name are “01” (for example,“102ALARM01”). The time correction value is subtracted from the timeindicated by preparing time data to obtain a value, which is used astime data for preparing the time order table (S277). The directory timeorder table is updated so as to include information as to the seconddirectory (S279), and the compressed image data is stored on the harddisk 7 so as to be positioned under the second directory (S273), wherebythe daylight saving time recording procedure is completed.

Reference is made to FIG. 7 again. The user manipulates manual buttons25 after the above procedure to give a command to stop processing to theCPU 11 via the system controller 23, the storage of compressed imagedata to the hard disk 7 is completed. Unless the command to stop isgiven, the procedure of steps S13 and the following are performedrepeatedly.

Although an embodiment of the present invention has been describedabove, the frame rate of 3 fps used for the image pickup unit, the harddisk used as an image data recording medium, the directory structure andnames shown in FIG. 5 and used for the hard disk and the JPEG method ofcompression for use in recording image data, etc. are solely intendedfor the illustration of one embodiment of the invention and are notlimitative to the invention.

1. A monitoring camera device wherein image capturing time data is addedto image data which is successive with respect to time, and the imagedata is stored on a recording medium, the monitoring camera device beingcharacterized in that a plurality of directories are prepared on therecording medium for containing a predetermined number of items of imagedata, each of the directories being given a name according to adirectory naming rule, wherein based on said naming rule, a portion ofsaid name is different based solely on when the directory is preparedduring the period of standard time versus when the directory is preparedduring the period of daylight saving time.
 2. A monitoring camera deviceaccording to claim 1 wherein each of the directories has attachedthereto directory preparing time data indicating the time when thedirectory is prepared.
 3. A monitoring camera device according to claim2 which comprises a processing unit for judging whether each of thedirectories is prepared during the period of the standard time or duringthe period of daylight saving time with reference to the name of thedirectory, and judging the order of directory preparing times using thetime indicated by the directory preparing data of the directory when thedirectory is found to have been prepared during the period of thestandard time, or using a value obtained by subtracting a timecorrection value from the time indicated by the directory preparing dataof the directory when the directory is found to have been preparedduring the period of daylight saving time.
 4. A monitoring camera deviceaccording to claim 3 which captures and records images while erasing thedirectory prepared earliest with reference to the result of judging thedirectory preparing time order.
 5. An image data management method for amonitonng camera device for continually capturing and recording imagesby preparing a plurality of directories on a recording medium, addingimage capturing time data to image data which is successive withrespective to time and storing the image data under the directories, theimage data management method comprising the steps of: preparingdirectories each having a name given thereto and directory preparingtime data attached thereto and indicating the time when the directory isprepared, a portion of the name being different based solely when thedirectory is prepared during the period of standard time versus when thedirectory is prepared during the period of daylight saving time, judgingwhether each of the directories is prepared during the period of thestandard time or during the period of daylight saving time withreference to the name of the directory, judging the order of directorypreparing times using the time indicated by the directory preparing dataof the directory when the directory is found to have been preparedduring the period of the standard time, or using a value obtained bysubtracting a time correction value from the time indicated by thedirectory preparing data of the directory when the directory is found tohave been prepared during the period of daylight saving time, anderasing the directory prepared earliest along with the image data underthe earliest directory with reference to the result of judging thedirectory preparing time order in the case where the number of directorshas reached an upper limit value.
 6. A monitoring camera device, whereinimage capturing time data is added to image data which is successivewith respect to time, and the image data is stored on a recordingmedium, the monitoring camera device being characterized in that aplurality of directories are prepared on the recording medium forcontaining a predetermined number of items of image data, each of thedirectories being given a name according to a directory naming rule,wherein based on said naming rule, a portion of said name is definedsolely depending on whether the directory is prepared during the periodof standard time or the period of daylight savings time.